Spline-Lock Plastic Pipe Joint With Molded Groove Restraint
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Solution Overview
Problem
Existing plastic pipe joining systems fail to withstand anticipated forces and are not cost-effective, particularly in applications requiring high tensile strength and resistance to hydraulic pressures, while maintaining air and water tightness.
Innovation Solution
A spline-type joining system using PEEK or PEEK reinforced with glass fiber for the keystrap and casing element, combined with a Rieber belling process, to create a secure and durable joint with improved tensile strength and pull-out resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If circumferential grooves are machined into the belled pipe end and spigot pipe end to receive a locking key strap, then the joint restraining capability is improved, but the manufacturing complexity and cost increase due to machining operations
Solution Approach 1:
The patent replaces the mechanical machining process with a mold-formed geometric feature. The hexagonal groove is created during the pipe extrusion/molding process itself, eliminating the need for subsequent machining operations. This substitution of manufacturing methods resolves the contradiction by maintaining the restraining capability while eliminating the complexity of machining operations.
Solution Approach 2:
The groove geometry is prepared in advance during the pipe manufacturing process, before the pipes need to be assembled. The mold forms the hexagonal groove directly into the pipe end during extrusion, so that when pipes are later joined, the restraining feature is already in place without requiring additional field operations or complex assembly procedures.
2Reliability
If a locking key strap is passed through the bell wall and around the circumferential passageway to restrain pipe separation, then the joint reliability under hydraulic forces is improved, but the device complexity increases due to additional components and assembly steps
Solution Approach 1:
The key strap serves multiple functions: it provides the restraining force to prevent pipe separation, it engages with the hexagonal groove to prevent rotation, and it creates a mechanical lock that resists pull-out forces. By making this single component multi-functional, the patent reduces the number of separate components needed while maintaining high reliability under various loading conditions.
Solution Approach 2:
The key strap is constructed from composite materials (aramid fibers in a polymer matrix) that provide high tensile strength and stiffness. This material choice allows a single component to withstand the combined stresses of hydraulic forces, mechanical locking, and rotational restraint, thereby maintaining reliability while minimizing component count.
3Reliability
If the spigot pipe end is inserted within the female belled pipe end with an elastomeric gasket for sealing, then the air and water tightness is improved, but the joint may separate under hydraulic forces without additional restraining mechanisms
Solution Approach 1:
The patent merges the sealing function and the restraining function into a single joint design. The elastomeric gasket provides the seal, while the hexagonal groove and key strap provide the mechanical restraint. These functions are combined in one integrated joint system rather than being separate components, allowing both sealing and force resistance to be achieved simultaneously.
Solution Approach 2:
The use of elastomeric materials for the gasket provides both sealing capability and some mechanical flexibility to accommodate the restraining forces. The composite key strap material provides high strength for restraint while the elastomeric gasket complements it with sealing and shock absorption, creating a composite joint system that handles both sealing and force resistance.
Data Source
AI summary
A restrained pipe joining system for plastic pipe is shown comprising male and female ends each having aligned circumferential grooves which form a canal for passage of a locking keystrap. The keystrap can be formed of PEEK or PEEK reinforced with glass fiber. During manufacture, the female belled end is sequentially formed over a Rieber style gasket and then over a ring-shaped casing member. The casing member is also formed from polymeric composite materials. In some cases, the casing is reinforced with an internal metal band.